[Mlir-commits] [mlir] c405fd3 - [mlir][acc] Fold present() clauses on device values (#212815)
llvmlistbot at llvm.org
llvmlistbot at llvm.org
Mon Aug 10 06:25:45 PDT 2026
Author: Ivan R. Ivanov
Date: 2026-08-10T15:25:40+02:00
New Revision: c405fd3870aadfce5a9cf1a13f0da8aaeb8d3854
URL: https://github.com/llvm/llvm-project/commit/c405fd3870aadfce5a9cf1a13f0da8aaeb8d3854
DIFF: https://github.com/llvm/llvm-project/commit/c405fd3870aadfce5a9cf1a13f0da8aaeb8d3854.diff
LOG: [mlir][acc] Fold present() clauses on device values (#212815)
The compiler must emit acc.device_ptr mapping for device values,
however, an existing present clause prevents that. A present on a device
value always holds, so fold it away to allow implicit data handling to
generate device_ptr mapping.
Added:
Modified:
mlir/lib/Dialect/OpenACC/Transforms/ACCImplicitData.cpp
mlir/test/Dialect/OpenACC/acc-implicit-data.mlir
Removed:
################################################################################
diff --git a/mlir/lib/Dialect/OpenACC/Transforms/ACCImplicitData.cpp b/mlir/lib/Dialect/OpenACC/Transforms/ACCImplicitData.cpp
index 628454905b488..5aae7dfef7d58 100644
--- a/mlir/lib/Dialect/OpenACC/Transforms/ACCImplicitData.cpp
+++ b/mlir/lib/Dialect/OpenACC/Transforms/ACCImplicitData.cpp
@@ -215,6 +215,7 @@
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/TypeSwitch.h"
+#include "llvm/Support/Casting.h"
#include "llvm/Support/ErrorHandling.h"
#include <type_traits>
@@ -457,15 +458,6 @@ Operation *ACCImplicitData::generateDataClauseOpForCandidate(
typeCategory, acc::VariableTypeCategory::aggregate);
Location loc = computeConstructOp->getLoc();
- if (acc::isDeviceValue(var)) {
- // If the variable is device data, use deviceptr clause.
- LLVM_DEBUG(llvm::dbgs() << "Using deviceptr clause because variable is "
- "device data\n");
- return acc::DevicePtrOp::create(builder, loc, var,
- /*structured=*/true, /*implicit=*/true,
- accSupport.getVariableName(var));
- }
-
Operation *op = nullptr;
op = getOriginalDataClauseOpForAlias(var, builder, computeConstructOp,
dominatingDataClauses);
@@ -490,6 +482,16 @@ Operation *ACCImplicitData::generateDataClauseOpForCandidate(
acc::getBounds(op));
}
+ if (acc::isDeviceValue(var)) {
+ // Variable is device data with no existing dominating mapping: use
+ // deviceptr clause.
+ LLVM_DEBUG(llvm::dbgs() << "Using deviceptr clause because variable is "
+ "device data\n");
+ return acc::DevicePtrOp::create(builder, loc, var,
+ /*structured=*/true, /*implicit=*/true,
+ accSupport.getVariableName(var));
+ }
+
if (isScalar) {
if (enableImplicitReductionCopy &&
acc::isOnlyUsedByReductionClauses(var,
@@ -702,6 +704,35 @@ static void insertInSortedOrder(SmallVector<Value> &sortedDataClauseOperands,
}
}
+/// A present() clause on a device value always holds. Erase it to allow the
+/// implicit data to generate an acc.deviceptr for it.
+template <typename OpT>
+static void foldPresentDeviceValue(OpT computeConstructOp) {
+ SmallVector<Value> remainingOperands;
+ SmallVector<acc::PresentOp> toErase;
+ for (Value var : computeConstructOp.getDataClauseOperands()) {
+ if (auto presentOp =
+ dyn_cast_if_present<acc::PresentOp>(var.getDefiningOp())) {
+ if (acc::isDeviceValue(presentOp.getVar())) {
+ toErase.push_back(presentOp);
+ continue;
+ }
+ }
+ remainingOperands.push_back(var);
+ }
+ if (toErase.empty())
+ return;
+
+ computeConstructOp.getDataClauseOperandsMutable().assign(remainingOperands);
+ for (acc::PresentOp presentOp : toErase) {
+ Operation *exitOp = findDataExitOp(presentOp);
+ assert(exitOp && exitOp->getNumResults() == 0);
+ presentOp.getAccVar().replaceAllUsesWith(presentOp.getVar());
+ exitOp->erase();
+ presentOp->erase();
+ }
+}
+
template <typename OpT>
void ACCImplicitData::generateImplicitDataOps(
ModuleOp &module, OpT computeConstructOp,
@@ -790,19 +821,24 @@ void ACCImplicitData::runOnOperation() {
acc::OpenACCSupport &accSupport = getAnalysis<acc::OpenACCSupport>();
+ SmallVector<Operation *> computeConstructOps;
module.walk([&](Operation *op) {
- if (isa<ACC_COMPUTE_CONSTRUCT_OPS, acc::KernelEnvironmentOp>(op)) {
- assert(op->getNumRegions() == 1 && "must have 1 region");
-
- auto defaultClause = acc::getDefaultAttr(op);
- llvm::TypeSwitch<Operation *, void>(op)
- .Case<ACC_COMPUTE_CONSTRUCT_OPS, acc::KernelEnvironmentOp>(
- [&](auto op) {
- generateImplicitDataOps(module, op, defaultClause, accSupport);
- })
- .Default([&](Operation *) {});
- }
+ if (isa<ACC_COMPUTE_CONSTRUCT_OPS, acc::KernelEnvironmentOp>(op))
+ computeConstructOps.push_back(op);
});
+
+ for (Operation *op : computeConstructOps) {
+ assert(op->getNumRegions() == 1 && "must have 1 region");
+
+ auto defaultClause = acc::getDefaultAttr(op);
+ llvm::TypeSwitch<Operation *, void>(op)
+ .Case<ACC_COMPUTE_CONSTRUCT_OPS, acc::KernelEnvironmentOp>(
+ [&](auto op) {
+ foldPresentDeviceValue(op);
+ generateImplicitDataOps(module, op, defaultClause, accSupport);
+ })
+ .Default([&](Operation *) {});
+ }
}
} // namespace
diff --git a/mlir/test/Dialect/OpenACC/acc-implicit-data.mlir b/mlir/test/Dialect/OpenACC/acc-implicit-data.mlir
index 3b6b5e1ade5e0..6551b20100005 100644
--- a/mlir/test/Dialect/OpenACC/acc-implicit-data.mlir
+++ b/mlir/test/Dialect/OpenACC/acc-implicit-data.mlir
@@ -287,3 +287,49 @@ func.func @test_declare_deviceptr_arg_in_parallel(%arg0: memref<?xi8>) {
// CHECK: acc.declare_exit token(%[[TOKEN]]) dataOperands(%[[DEVPTR]] : memref<10xf32>)
// CHECK-NOT: acc.copyin
// CHECK-NOT: acc.copyout
+
+// -----
+
+// Fold an explicit present of device data: drop present/delete and rewrite
+// region uses; subsequent implicit mapping should emit deviceptr.
+func.func @test_fold_present_device_value() {
+ %alloc = memref.alloca() : memref<10xf32, #gpu.address_space<global>>
+ %present = acc.present varPtr(%alloc : memref<10xf32, #gpu.address_space<global>>) -> memref<10xf32, #gpu.address_space<global>> {name = "a"}
+ acc.parallel dataOperands(%present : memref<10xf32, #gpu.address_space<global>>) {
+ %c0 = arith.constant 0 : index
+ %load = memref.load %present[%c0] : memref<10xf32, #gpu.address_space<global>>
+ acc.yield
+ }
+ acc.delete accPtr(%present : memref<10xf32, #gpu.address_space<global>>) {dataClause = #acc<data_clause acc_present>, name = "a"}
+ return
+}
+
+// CHECK-LABEL: func.func @test_fold_present_device_value
+// CHECK: %[[ALLOC:.*]] = memref.alloca() : memref<10xf32, #gpu.address_space<global>>
+// CHECK: %[[DEVPTR:.*]] = acc.deviceptr varPtr(%[[ALLOC]] : memref<10xf32, #gpu.address_space<global>>) -> memref<10xf32, #gpu.address_space<global>> {implicit = true, name = ""}
+// CHECK: acc.parallel dataOperands(%[[DEVPTR]] : memref<10xf32, #gpu.address_space<global>>) {
+// CHECK: memref.load %[[DEVPTR]][{{.*}}] : memref<10xf32, #gpu.address_space<global>>
+// CHECK-NOT: acc.present
+// CHECK-NOT: acc.delete
+
+// -----
+
+// Present of host data must not be folded away.
+func.func @test_present_host_not_folded() {
+ %alloc = memref.alloca() : memref<10xf32>
+ %present = acc.present varPtr(%alloc : memref<10xf32>) -> memref<10xf32> {name = "a"}
+ acc.parallel dataOperands(%present : memref<10xf32>) {
+ %c0 = arith.constant 0 : index
+ %load = memref.load %present[%c0] : memref<10xf32>
+ acc.yield
+ }
+ acc.delete accPtr(%present : memref<10xf32>) {dataClause = #acc<data_clause acc_present>, name = "a"}
+ return
+}
+
+// CHECK-LABEL: func.func @test_present_host_not_folded
+// CHECK: %[[ALLOC:.*]] = memref.alloca() : memref<10xf32>
+// CHECK: %[[PRESENT:.*]] = acc.present varPtr(%[[ALLOC]] : memref<10xf32>) -> memref<10xf32> {name = "a"}
+// CHECK: acc.parallel dataOperands(%[[PRESENT]] : memref<10xf32>) {
+// CHECK: memref.load %[[PRESENT]][{{.*}}] : memref<10xf32>
+// CHECK: acc.delete accPtr(%[[PRESENT]] : memref<10xf32>) {dataClause = #acc<data_clause acc_present>, name = "a"}
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